The primary objective of the proposed research is to estimate the supply of immigrants to the U.S. This supply would be estimated specifically for various age classes of immigrants, for particular source countries of immigrants, and under various assumptions regarding quota restrictions in the U.S. We also plan to study the effects that past changes in U.S. immigration quotas have had on the occupational and age composition of immigration flows. The models that underlie the empirical work emphasize the importance both of differential economic advantage and the transactions cost connected with international migration. Estimation of the models we propose involves a number of difficulties, among which the problems associated with U.S. quota restrictions rank high. We suggest several possible econometric approaches, including the analysis of international flows within the European Economic Community, the Brithish Commonwealth, and the U.S. and its territories, where during certain periods migration has been institutionally unconstrained. We also plan to examine the effects of the 1962 changes in Canadian immigration restrictions. These changes constituted a divergence from U.S. policies and from previous Canadian policies by emphasizing labor considerations rather than family reunification. Despite a recent flurry of research activity directed at international migration and motivated by Congressional interest in reconsidering U.S. immigration policy, many of the most fundamental questions regarding immigration and the U.S. economy remain unanswered. This research effort constitutes an effort to address certain of these questions.